Field of the Disclosure
Embodiments of the present invention relate to an organic light emitting display device, and more particularly, to an organic light emitting display device with a thin film transistor of a top gate structure.
Discussion of the Related Art
An organic light emitting display device, which emits light in itself, is provided in such a structure in which a light emitting layer is formed between a cathode for injecting electron and an anode for injecting hole. When the electron generated in the cathode and the hole generated in the anode are injected into the inside of the light emitting layer, an exciton is produced by the electron and hole bond. Then, when the exciton falls to a ground state from an excited state, the organic light emitting display device emits light.
The organic light emitting display device includes a thin film transistor which functions as a switching device. The thin film transistor may be classified into a bottom gate structure and a top gate structure. In case of the bottom gate structure, a gate electrode is disposed below an active layer. Meanwhile, in case of the top gate structure, a gate electrode is disposed above an active layer.
Hereinafter, a related art organic light emitting display device with a thin film transistor of a top gate structure will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view illustrating a related art organic light emitting display device.
As shown in FIG. 1, the related art organic light emitting display device may include a substrate 10, an active layer 20, a gate insulating film 25, a gate electrode 30, an insulating interlayer 35, a source electrode 40a, a drain electrode 40b, a passivation film 45, a planarization film 50, an anode 60, a bank layer 70, an organic emitting layer 80, and a cathode 90.
The active layer 20 functions as an electron transfer channel, and the active layer 20 is formed on the substrate 10. The gate insulating film 25 insulates the active layer 20 and the gate electrode 30 from each other, and the gate insulating film 25 is formed on the active layer 20. The gate electrode 30 is formed on the gate insulating film 25.
The insulating interlayer 35 is formed on the gate electrode 30. The insulating interlayer 35 is formed on the surface of the substrate 10, wherein the insulating interlayer 35 has a first contact hole for exposing one end of the active layer 20 and a second contact hole for exposing the other end of the active layer 20.
The source electrode 40a and the drain electrode 40b are formed on the insulating interlayer 35. The source electrode 40a is connected with the one end of the active layer 20 through the first contact hole, and the drain electrode 40b is connected with the other end of the active layer 20 through the second contact hole.
The passivation film 45 is formed on the source electrode 40a and the drain electrode 40b, wherein the passivation film 45 protects a thin film transistor provided therebelow. The planarization film 50 is formed on the passivation film 45, to planarize the surface of the substrate 10. The passivation film 45 and the planarization film 50 have a contact hole to expose the source electrode 40a therethrough.
The anode 60 is formed on the planarization film 50. The anode is connected with the source electrode 40a through the contact hole provided in the passivation film 45 and the planarization film 50. The bank layer 70 is formed on the planarization film 50. The bank layer 70, which is formed in a matrix configuration, defines a display area for displaying an image.
The organic emitting layer 80 is formed on the anode 60. The organic emitting layer 80 is formed in the display area defined by the bank layer 70. The cathode 90 is formed on the organic emitting layer 80.
In case of the related art organic light emitting display device, the active layer 20 is formed right on the upper surface of the substrate 10. Accordingly, the active layer 20 is exposed to external light being incident through the lower surface of the substrate 10, to thereby deteriorate reliability of the active layer 20.